For example, JP 2001-181327A (corresponding to US 2001/0020075A) discloses an ethylene-hexene copolymer having weight average molecular weight (Mw) of 97,000, which is produced using an olefin polymerization catalyst formed by contacting with one another bis(pentafluorophenoxy)zinc, ethylenebis(indenyl)zirconium chloride, and triisobutylaluminum.